In a large bowl, mix the mustard, oil, honey, lemon juice, garlic, and a pinch of salt and pepper, until they are well-combined. Add the chicken breasts, coating them entirely, and allow them to marinate for 2-3 hours.

Once chicken breasts have marinated, grill (you can also use a grill pan) on both sides until chicken is cooked through.

Allow chicken to cool for 10 minutes before chopping into 1/2-inch chunks.

For the Honey Mustard Dressing

While the chicken is marinating, make the dressing: mix the mustard, lemon juice, honey, salt, and pepper in a blender or food processor. While the mixture is blending, slowly drizzle in the oil. Blend just until everything is well-mixed. Chill dressing until ready to use.

To Assemble the Lettuce Cups

In one lettuce leaf, add chicken, a bit of bacon, a few cherry tomatoes, a few pieces of avocado, and a sprinkling of green onions.

Serve lettuce cups drizzled with honey mustard dressing (or serve dressing on the side for dipping).